<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .box1 {
        margin-bottom: 20px;
        width: 200px;
        height: 200px;
        background-color: deepskyblue;
        padding: 5px;
        border: 5px solid black;
        /* 默认是标准模型 */
        box-sizing: content-box;
      }

      .box2 {
        width: 100px;
        height: 100px;
        background-color: lightblue;
        padding: 5px;
        border: 5px solid black;
        /*  怪异盒模型 */
        box-sizing: border-box;
      }
    </style>
  </head>

  <body>
    <div class="box1"></div>
    <div class="box2"></div>
  </body>
</html>
